Cytokine amplification and inhibition of immune and inflammatory responses.

Cytokines are soluble mediators of intercellular communication. They contribute to a chemical signalling language that regulates development, tissue repair, haematopoiesis, inflammation and the immune response. Potent cytokine polypeptides have pleiotropic activities and functional redundancy. They act in a complex network where one cytokine can influence the production of, and response to, many other cytokines. In the past 5 years this bewildering array of 100+ effector molecules and associated cell surface receptors has been simplified by study of three-dimensional cytokine and cytokine receptor structure: elucidation of convergent intracellular signalling pathways; and molecular genetics, especially targeted gene disruption to 'knockout' production of individual cytokines in mice. It is also now clear that much of the pathophysiology of infectious disease can be explained by the induction of cytokines and the subsequent cellular response. Cytokine and cytokine antagonists have also shown therapeutic potential in a number of chronic and acute diseases.